As light emitting diodes (LEDs), particularly blue or ultraviolet (UV) LEDs having an emission wavelength of approximately 250 nm to 550 nm, high-brightness products using a compound semiconductor made of a GaN-based material such as GaN, GaAlN, InGaN or InAlGaN have been developed. Therefore, it is possible to form a high-definition full-color image using a technique of combining the above-described blue LEDs with red and green LEDs. For example, a white LED can be produced by combination of the blue or UV LED with a fluorescent material. Such a white LED is expected to be used for backlights of a liquid crystal display device (LCD) or general lightings.
As described above, an epoxy resin including an acid anhydride-based curing agent and thus having a high adhesive property and excellent dynamic durability has been widely used in the art as an encapsulation material for a red, green, blue or UV LED. However, the epoxy resin-based encapsulation material has problems in that it has low transmittance with respect to light ranging from blue to UV wavelength ranges and also shows poor light resistance, such as discoloration caused by degradation due to light. Accordingly, a technique associated with the epoxy resin encapsulation material has been proposed to solve the above-mentioned problems (for example, Japanese Patent Laid-open Publication Nos. Hei 11-274571, 2001-196151 or 2002-226551).
However, the epoxy resin encapsulation materials as described in the above-mentioned patent documents have a problem in that they still show poor light resistance.
Meanwhile, attention has been drawn to a silicone resin as a material having excellent light resistance at a low wavelength range. However, the silicone resin has problems in that its heat resistance representative of a glass transition temperature may be degraded, its surface has a tack property, a foreign substance such as dust may be easily attached to a cured product due to static electricity since the cured product has very high resistivity, and properties such as transparency may be easily degraded.